Ultrasonic transducers are used in a wide variety of contexts including, but not limited to, oil and gas applications, non-destructive testing, and the medical field. Ultrasonic transducers generally operate by outputting an ultrasonic pulse or vibration in a direction of an object or area to be sensed, and detecting echoes of the original ultrasonic pulse reflected off the object or another point in the sensor range. To accomplish this, ultrasonic transducers typically include a piezoelectric element, positioned between two electrodes, designed to generate the ultrasonic pulse when a voltage is applied across the electrodes. The piezoelectric element may also move in response to the ultrasonic echoes reaching the transducer, and this movement can generate a current across the electrodes that is used to determine a distance from the transducer to the sensed object. In order to generate a clean ultrasonic pulse, such ultrasonic transducers typically include a backing material positioned near the piezoelectric element to reduce reverberations inside the transducer.
In traditional borehole operations, ultrasonic transducers are often equipped with a backing material made of tungsten-rubber to dampen internal reverberations generated by the piezoelectric element of the transducer. Unfortunately, there are certain disadvantages associated with the use of tungsten rubber backing materials in transducers, and particularly those transducers used in borehole operations. For example, it can be difficult to produce a consistent and sizable homogeneous tungsten-rubber mixture for the backing material, which makes such mixtures expensive and laborious to produce. In addition, it can be challenging to optimize the properties of the backing material so that the backing material matches a mechanical impedance of the piezoelectric element and operates with a desired attenuation coefficient. These two properties often compete with each other in existing ultrasonic transducers. Further, the mechanical properties of the rubber in the tungsten-rubber mixture can change dramatically as borehole temperature rises, which can lead to a poor coupling between the piezoelectric element and the tungsten-rubber backing material. Still further, as temperature rises in borehole applications, the effects on the tungsten-rubber mixture can reduce the capability of dampening the reverberations from the piezoelectric element via the backing material. There can also be significant changes in the attenuation coefficient of the backing material as the rubber matrix gets softer at higher temperatures.